The objective of this study is to assess the safety and maximum tolerated dose of rhIL-12 administered by subcutaneous injection in patients with cancer. Preliminary observations on response to therapy will include the determination of immunopharmacologic profile of rhIL-12 and the anti-tumor efficacy. In addition, pharmacokinetic measurements of the serum concentrations of rhIL-12 administered as a subcutaneous injection will be obtained in a selected subset of patients.